1. Field of the Invention
The invention relates to a combined generator with built-in eddy-current magnetic resistance, and more particularly to a generator that employs an outward turning type inertia flywheel to form a self-generated supply system. Meanwhile, one or several solenoids for producing the eddy-current magnetic resistance are integrally formed on the internal circumference of the stator iron core.
2. Description of the Related Art
The direct application of the automotive generator to the fitness apparatus and the rehabilitation apparatus that serves as a resistance system is traced back to the American fitness apparatus at the early stage. The American automotive industry is well developed. Meanwhile, the generator employed in the fitness apparatus was not popular. Therefore, no generator specially designed for the fitness apparatus is available. Due to the easy access and the mature technique, most of the fitness apparatus assembly manufacturers employed the automotive generator to be power supply and resistance source of the fitness apparatus. However, the automotive generator is not designed specially for the fitness apparatus. As a result, there are many parts that do not comply with the features of the fitness apparatus. This will be described as follows:
Generally, the automotive engine requires a higher rotational speed. Therefore, the problem of efficiency of the low rotational speed is often neglected when the automotive generator is developed. To the contrary, the fitness apparatus and the rehabilitation apparatus just require the low rotational speed. In order to obtain a higher efficiency under the low rotational speed, the fitness apparatus manufacturers tried to enhance the rotational speed for fulfilling the requirement of high rotational speed of the automotive generator. The rise of the rotational speed of the generator results in the increase of the efficiency. However, other problems appear:
1. In order to achieve the rise of the rotational speed, the one-stage transmission has to be changed in a two-stage transmission, thereby increasing the manufacturing difficulty and cost.
2. The high rotational speed causes a greater resonance and magnetic sound. It is much unfavorable for the people to use the fitness apparatus and the rehabilitation apparatus indoors since they normally do not like noise to disturb their mood.
3. Unlike the fitness apparatus, the automotive generator does not require the application of inertia. Therefore, no inertia flywheel is installed in the automotive generator. However, the automotive generator employed in the fitness apparatus brings the operator an uncomfortable feeling in using the apparatus.
4. The automotive generator has a greater length so that the vehicle body of the fitness apparatus and the rehabilitation apparatus is correspondingly wider. Therefore, the feet of the operator have to be opened to a greater extent, thereby causing discomfort in use.
As shown in FIGS. 1A and 1B, the generator used as resistance system of fitness apparatus includes a shaft 11 passing through an inertia flywheel 12 and a magnet core 14. A plurality of generating coils 15 is disposed on the circumference of the magnet core 14. A generator 10 is formed when the inertia flywheel 12 and the permanent magnets 13 on the internal side thereof are rotated. Such a structure is disclosed in U.S. Pat. Nos. 4,775,145, 5,558,624, 5,236,069, etc. In comparison with the automotive generator, it is more suitable for the application to the fitness apparatus and the rehabilitation apparatus. Advantages thereof are described as follows:
1. The form is flat and suitable for the fitness apparatus and the rehabilitation apparatus. Meanwhile, the vehicle body can be designed in a flat form so that it is not necessary for the operator to open his feet greatly. As a result, a comfortable feeling in taking exercise can be obtained.
2. The structure is designed specially for the fitness apparatus. Therefore, an inertia flywheel is available for providing sufficient inertia that ensures a smooth movement.
However, it still has the following inevitable drawbacks:
1. The resistance source is mainly resulted from the reverse connection of the power source of the generator. When the resistance is required, the type of the original generator is converted into the type of an electric motor, thereby creating a force opposite to the movement direction for achieving a braking effect. However, this braking effect is not enough. In order to eliminate this drawback, the speed ratio has to be enlarged by increasing the rotational speed of the generator. Nevertheless, the increase of the speed ratio will create the drawbacks as depicted in points 1 and 2 of the automotive generator.
2. The vibration and the noise created by multiple resonance of the reverse connection of power depicted in point 1 will be more intensified.
3. The power of the generator is not always effectively utilized. In other words, one part of the power must be consumed and lost. Therefore, a great resistance has to be installed for consuming the redundant power, thereby increasing the cost and lowering the efficiency.
Another composite generator includes a solenoid 16 and a magnet core 17. The structure is illustrated in FIGS. 2A and 2B and disclosed in U.S. Pat. No. 6,084,325. This structure employs the redundant power of the generator to create the braking force as the resistance for the fitness apparatus and the rehabilitation apparatus. In this way, the drawbacks of the above-mentioned two products can be effectively removed. In other words, this structure successfully changes two-stage transmission of the fitness apparatus and the rehabilitation apparatus of the generator into one-stage transmission, thereby considerably reducing the production cost and lowering the demand on the vehicle body. The advantages and the disadvantages are shown as follows:
Advantages:
1. The efficiency is effectively increased such that the two-stage transmission of the fitness apparatus and the rehabilitation apparatus is changed into one-stage transmission, thereby ensuring a great reduction of cost.
2. The demand on the precision of the vehicle body is decreased due to the one-stage transmission, thereby reducing the failure rate of the whole vehicle.
3. The rotational speed of the generator is low due to the one-stage transmission, thereby effectively minimizing the resonance and the noise.
4. The flat structure is favorable for the design of the vehicle body and suitable for the fitness apparatus and the rehabilitation apparatus. In other word, the vehicle body can be made flatter. Meanwhile, it is not necessary for the operator to open his feet widely, thereby ensuring a comfortable exercise.
Disadvantages:
1. The fixed structure: A higher performance is only available when a uniform gap between the solenoid 16 (as well as the magnet core 17) and the inertia flywheel 12. Due to the fixed structure, the dimensions of the generator are not changeable according to the demand of each operator.
2. The magnet core 14 and the magnet core 17 of the generator are two separate and independent systems so that the production cost is higher.
3. The solenoid 16 is a separate body installed outside the inertia flywheel 12 so that the volume thereof is greater. This is unfavorable for the design of the whole vehicle body.
The above-mentioned systems have their own advantages and disadvantages. Therefore, we keep the advantages of all systems and improve the disadvantages. It is expected to resolve the above-mentioned problems.